The present invention relates to a wheel suspension for steerable wheels of motor vehicles, especially for rear wheels, with a wheel carrier supporting the wheel which is connected with the vehicle body or the like by way of several wheel guide members, of which one acts as steering tie rod and is displaceable by an adjusting motor.
In wheel suspensions for steerable front wheels, it is quite generally customary to cause a tie rod displaceable approximately in its longitudinal direction and extending approximately transversely to the vehicle longitudinal direction to engage at a steering lever rigidly connected with the wheel carrier. This type of construction also has already been suggested on several occasions for rear wheels (for example, DE-OS Nos. 33 38 389 or 34 46 881), when these rear wheels are to be steerable in addition to the front wheels.
It is further known (DE-OS No. 34 37 071) to cause adjusting cylinders to engage at an auxiliary frame which supports the inclined guide members and is further connected with the vehicle body by way of rubber elements. If the adjusting cylinders are actuated, a limited rotation of the auxiliary frame and therewith also of the wheels supported by way of the inclined guide members about a vertical axis is possible, however, only to a very limited extent within the scope of the elasticity of the rubber bearings.
The requirement exists for reasons of the available installation space as also for kinematic and elastokinematic reasons to assign to a cross guide member supporting the support spring, for example, the further function to act also as tie rod. Such a cross guide member then not only transmits--as a customary tie rod--forces in the direction of the axis of the tie rod, but also additional forces in an approximately vertical direction owing to the very high support force of the support spring. As a result thereof, the actuating member driven by the adjusting motor, at which the inner end of the cross guide member is pivotally connected, is also subjected to very high vertical forces. This entails an increased wear of this pivotal connection or jointed connection and compels a particularly large dimensioning thereof. The loads of the steering transmission device (hydrocylinder, adjusting motor, hydromotor, rack-and-pinion steering gear and the like) conditioned by the considerably higher forces lead to an increased friction and therewith to unfavorable control, respectively, response behavior (breakaway forces). Furthermore, an increased steering power requirement is necessary.
Finally, it would be very difficult with a direct control of a cross guide member to take any influence, for example, on the steering angle ratio of the wheel on the inside of the curve in relation to the wheel on the outside of the curve (Ackermann angle).
The present invention is therefore concerned with the task to provide a wheel suspension of the aforementioned type which requires relatively little structural space while avoiding a separate tie rod, has a favorable response behavior and keeps away excessive forces from the actuating members of the adjusting motor.
The underlying problems are solved according to the present invention in a wheel suspension according to the aforementioned type in that the displaceable wheel guide member is a guide member supporting the support spring, which with its inner end is pivotally connected at an intermediate lever that is pivotal at the vehicle body or the like about a pivot axis extending at least approximately in the vehicle longitudinal direction as well as is connected with the adjusting motor. In this manner, the vertical forces transmitted from the support spring to the guide member are not further transmitted to the actuating members of the adjusting motor but are absorbed by the intermediate lever. Furthermore, the position of the intermediate lever can thereby be so selected that also transverse forces which stem from an inclined position of the support spring as viewed in longitudinal elevation, do not act on the adjusting motor at least in the normal position of the motor vehicle. The intermediate lever also permits it to provide a force step-down between the adjusting motor and the guide member, whereby both the load on the steering device as also the required adjusting force are reduced. A displacement transmission also results therefrom which with a regulated manner of operation of the adjusting motor may provide regulating technical advantages by reason of the increase of the regulating distances. By selection of an appropriate angle of the two intermediate levers of an axle, it is finally possible to cause the wheel on the inside of the curve to carry out a greater steering deflection than the wheel on the outside of the curve so that the lateral force potential of both wheels is fully exhausted.